Yuri Wedmid

An improved procedure for the synthesis of choline phospholipids via 2-bromoethyl dichlorophosphate.

Choline phospholipids can be conveniently synthesized by reaction of a lipophilic alcohol, such as diacylglycerol, with 2-bromoethyl dichlorophosphate followed by nucleophilic displacement of the bromine with trimethylamine. We found that the low yields often encountered in the initial phosphorylation step are particularly due to exchange of both chlorines for alkoxy functions (triester formation) and to chlorination of the alcohol by 2-bromoethyl dichlorophosphate. However, these drawbacks can be overcome by proper choice of the reaction medium and by optimizing other reaction conditions. The procedure described is efficient and most versatile, and it lends itself to the preparation of a wide range of choline phospholipids containing a glycerol, diol, or long-chain alkyl backbone and bearing various aliphatic functions. Proton and carbon-13 nuclear magnetic resonance spectroscopy proved useful in establishing the homogeneity and structures of the synthetic intermediates and byproducts and of the choline phospholipids synthesized.

24-nor-5β-chol-22-enes derived from the major bile acids by oxidative decarboxylation

The preparation of 24-nor-5beta-chol-22-enes from formyloxy-5beta-cholanic acids by oxidative decarboxylation with lead tetraacetate is described. NMR data is presented with other physical constants for the norcholenes derived from cholic, chenodeoxycholic, ursodeoxycholic, hyodeoxycholic, and deoxycholic acids. The facile synthesis of these norcholenes demonstrates the applicability of the formyloxy protecting group to oxidative decarboxylations in the bile acid series.

Lipid organization in peripheral nerve: Natural abundance carbon-13 NMR spectroscopy on intact tissues

Summary Native structures of peripheral nerve myelin can directly be observed by carbon-13 nuclear magnetic resonance (NMR) spectroscopy after dissecting epineurial and perineurial tissue sheaths from the endoneurium. NMR spectra of the intact endoneurial tissue describe a highly ordered and largely immobilized lipid phase in the myelin membrane which is in marked contrast to the fluid-like lipid distribution in the intracellular lipid droplets of epineurium and perineurium. Membrane reconstitution experiments with total endoneurial lipids, but without protein, suggest a primary role of the lipids in myelin bilayer assembly. Reconstitution experiments also indicate that polar lipid-protein interactions in native myelin involve the CH2-N function of choline phospholipids, in particular.

15-Methyl-1,2-hexadecanediol, a major constituent of hamster surface wax

Long chain 1,2-alkanediol diesters comprise about 15–20% of the acetone soluble skin surface wax of golden Syrian hamsters. The constituent 1,2-alkanediols, obtained through acidic methanolysis, were fractionated by preparative gas liquid chromatography of their isopropylidene derivatives. The major component (57%) was identified by nuclear magnetic resonance and mass spectrometry as 15-methyl-1,2-hexadecanediol.